Cleaning oxide from oxidized molybdenum wire



Patented Jan. 20, 1953 UNITED STATES TENT OFFICE CLEANING OXIDE FROMOXIDIZED MOLYBDENUM WIRE Marie A. Levesque, Peabody, Mass.

2 Claims.

This invention relates generally to treatment of the surface only of amaterial with a combination of chemicals with which the material itselfreacts, and in particular relates to cleaning oxide from the surface ofa metal, which may be for example, molybdenum.

An object of the invention is to clean from the surface of, or otherwiseaffect the surface of, a material without affecting the body of thematerial itself. A particular object is to remove oxide from an oxidizedmolybdenum wire without removing any appreciable amount of themolybdenum wire itself.

A feature of the invention is the dipping of a material into a chemicalbath, and then while still wet with the first chemical, dipping it intoa second chemical bath.

A particular feature is the clipping of a metal wire into a bath ofnitric acid solution and then while the metal is still wet with thenitric acid solution, dipping it into a solution of hydrochloric acid.

Other features, objects and advantages of the invention will be apparentfrom the following description.

In the use of molybdenum wire in electric lamps and the like, it isdesired to have the surface extremely clean of all impurities such asoxides and the like, and in many cases the molybdenum wire as receivedmay have a heavy film of oxide. My invention avoids the considerablecorrosive effect which the usual cleaning baths have on the metalitself.

In cleaning oxidized molybdenum wire, for example, according to myinvention, I dip the wire in a solution of nitric acid, which may be,for example, 3 parts water and 8 parts nitric acid. Such a solution willhave a specific gravity of about 1.15.

After dipping the wire in the nitric acid for about 10 seconds I removeit from that solution and immediately dip it into a solution ofhydrochloric acid, the solution being, for example, about 3 parts acidand 8 parts water, having a specific gravity, for example, of about1.05. The wire is left in the solution for about 10 seconds, and isplaced immediately in water, agitating for a few seconds.

If this does not remove all the oxide, the process may be repeated.

The solutions should be at nearly their boiling point for best results.

When the oxide is all removed, the wire should be rinsed in water.

The process is extremely effective, and its action appears to be asfollows: After dipping in the nitric acid bath, the metal carries a filmof acid over into the hydrochloric acid and momentarily gives a combinedsolution of great oxidizing power to the formation of free chlorine andchlorine compounds. This lasts only momentarily and the products aresoon dispersed in the hydrochloric acid, thereby effectively stoppingany further action on the metal itself. My method is therefor selfregulating, in that its action stops automatically before corroding theunderlying metal appreciably.

The quantity of the second solution in which the metal is dipped, shouldof course, be very great in comparison with the amount of solutionremaining on the metal from being dipped in the first solution.

Although I have described the invention with respect to the foregoingparticular embodiment, it is also applicable to other cases wherechemical action on a surface is desired and automatic termination of theaction is desired before any great penetration of the surface. It may beused where a bath containing a number of ingredients is more effectivethan a bath of fewer ingredients, so that certain of the ingredients maybe present in the first bath, and the remainder in the second.

What I claim is:

1. The method of cleaning oxide from an oxidized molybdenum wire, saidmethod comprising: dipping said wire into a solution of nitric acid,removing the wire from said solution, dipping it into a solution ofhydrochloric acid while the wire is still wet with the nitric acidsolution, removing the wire from said solution and washing the wire withwater.

2. The method of claim 1, in which the solutions used are eachapproximately half acid and half water.

MARIE A. LEVESQUE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 145,971 Sawyer Dec. 30, 18732,365,153 Stevens Dec. 19, 1944 2,410,322 Weesner Oct. 29, 19462,538,702 Noble Jan. 16, 1951

1. THE METHOD OF CLEANING OXIDE FROM AN OXIDIZED MOLYBDENUM WIRE, SAIDMETHOD COMPRISING: DIPPING SAID WIRE INTO A SOLUTION OF NITRIC ACID,REMOVING THE WIRE FROM SAID SOLUTION, DIPPING IT INTO A SOLUTION OHHYDROCHLORIC ACID WHILE THE WIRE IS STILL WET WITH THE NITRIC ACIDSOLUTION, REMOVING THE WIRE FROM SAID SOLUTION AND WASHING THE WIRE WITHWATER.